mtDNA and AFLP markers demonstrate limited genetic differentiation within the Pyganodon cataracta – Pyganodon fragilis freshwater mussel complex in Atlantic Canada

• Published in: Canadian Journal of Zoology
• Main Authors: Stanton, L.M., Hoeh, W.R., McAlpine, D.F., Hebda, A., Stewart, D.T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2012
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Canada; Lamarck; Newfoundland
• Online Access: http://dx.doi.org/10.1139/z2012-100; http://www.nrcresearchpress.com/doi/full-xml/10.1139/z2012-100; http://www.nrcresearchpress.com/doi/pdf/10.1139/z2012-100

Two nominal species of freshwater mussels, Pyganodon cataracta (Say, 1817) (eastern floater) and Pyganodon fragilis (Lamarck, 1819) (Newfoundland floater), occur in Atlantic Canada, but their taxonomic status has been controversial. We analyzed the female-transmitted mitochondrial cytochrome c oxidase subunit I (i.e., FCOI) and nuclear internal transcribed spacer region (ITS-1) gene sequences, as well as multilocus amplified fragment length polymorphism (AFLP) markers, to evaluate genetic variation in Pyganodon specimens from Atlantic Canada. We found that Pyganodon samples from this region displayed no or extremely low (i.e., <0.5%) genetic divergence for ITS-1 and FCOI sequence data, respectively. Inferences from nested clade analysis of FCOI haplotypes suggest restricted gene flow with isolation by distance and contiguous range expansion. Analysis of molecular variance inferred from presence or absence of nuclear-encoded AFLP bands showed moderate geographic structuring among provinces but no correspondence between mtDNA haplotypes and AFLP profiles. Similarly, there was no correspondence between presence of a single or a double loop on the umbo and FCOI haplotype. These mtDNA and AFLP markers demonstrate limited genetic differentiation within the Pyganodon cataracta–Pyganodon fragilis freshwater mussel complex in Atlantic Canada and question the species-level distinctness of these putative taxa.